This discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to a helical conveyor, comprising a drivable endless conveyor belt having a transport section for transporting products where the conveyor belt follows at least partly a helical path between a lower end and an upper end of the transport section and a return section where the conveyor belt follows a path between the lower end and the upper end outside the transport section, a lower end reverse guide for turning the conveyor belt upside down and reverting its direction of movement between the transport section and the return section at the lower end of the transport section and an upper end reverse guide for turning the conveyor belt upside down and reverting its direction of movement between the transport section and the return section at the upper end of the transport section, wherein the return section leaves the upper end through a horizontally oriented upper return section portion and the return section leaves the lower end through a horizontally oriented lower return section portion.
Helical conveyors are widely known in the prior art. In general a helical conveyor has an endless conveyor belt which follows a helical transport path for transporting products in vertical direction from an input at the lower end to an output at the upper end of the helical path and a return path along which the conveyor belt moves back from the output to the input. Hence, products may be supplied to the conveyor belt at the input and removed from the conveyor belt at the output, whereas the unloaded belt moves back from the output to the input.
A typical known helical conveyor has its output at a higher level than its input. At the output the conveyor belt leaves the helical path and follows a straight horizontal path before it bends downwardly by an angle of 90° outside the helical path, as seen from above. After arriving at a height level near the input the conveyor belt bends again by an angle of 90° and follows a straight horizontal path extending parallel to and below the horizontal path at the output. Subsequently, the conveyor belt bends upwardly via a reverse roller and reverts at the input in order to follow the helical path from the input to the output. This means that the conveyor belt outside the helical path follows a short track, whereas the bends of the conveyor belt about an axis extending perpendicularly to its conveying direction and parallel to the plane of the conveyor belt, are always directed in the same direction, i.e. the conveyor belt is always bent about its lower side, hence in a direction from the upper belt side to the lower belt side about an axis extending transversely to the conveying direction. This may be advantageous for certain conveyor belts which have a smaller minimum bending radius about their lower side than about their upper side, such that small-radius bends can be applied.
A drawback of the latter conveyor is the presence of a straight portion of the conveyor belt downstream of the output at the upper end of the helical path. For example, if it is desired to stack two helical conveyors onto each other and to connect the output of one of them to the input of the other one, the upper conveyor must have a horizontal displacement with respect to the lower conveyor due to the straight portion downstream the upper end of the helical path of the lower conveyor. Furthermore, if two conveyor belts are applied parallel to each other, their straight portions lead to a difference between the linear speed and the rotational speed between the parallel conveyor belts, which may cause opposite friction forces onto products to be transported by both belts.
In another known type of a helical conveyor straight portions at the input and the output of the helical path are minimized, caused by reverse rollers at the input and output which turn the conveyor belt upside down, whereas the conveyor belt is guided below the transport path such that the return path also follows a helical path, i.e the same path as the helical transport section but in opposite direction, as seen from above. This configuration is advantageous in terms of compactness, but requires a relatively long conveyor belt causing a relatively high friction rate.